I have read somewhere that not all Coticules are equally suitable for razor honing. Is this true?

There are differences in Coticules, mainly in speed, and - correlating to that - the sharpness level you can manage to get from the hone when it's used with slurry (an abrasive milk formed by a mixture of water and stone particles that are released by rubbing the surface with a smaller piece of Coticule). After the slurry stage, Coticules are always used with just water to refine the edge further and achieve the maximum keenness that can be reached. If done correctly that keenness will always be more than adequate for a smooth shave without any "pulling" discomfort.During the slurry phase, faster Coticules level off on a less sharp limit than those who approach their goal at a slower pace. This happens because there is a higher concentration of abrasive garnets present in the slurry of fast Coticules and presumably they are also more aggressive. These garnets impact with the very tip of the edge, which causes it to loose some of its definition. The keener and fragile the edge becomes during the honing, the more it is affected by this process.Slower Coticule display less off this behavior, and they generally do leave a sharper edge, coming right off the slurry stage.But either way, slow or fast, the edge won't be keen enough for a comfortable shave after honing on slurry. The slurry is just used to vastly speed up the first part of the honing. You always have to finish on plain water, preferably after some additional procedure to bridge the gap between the speed of slurry and the very slowly developing superior edge on plain water. There are several different options to pursue that, and they are presented in the razor honing articles found on www.Coticule.be Most Coticules that abrade steel fast with slurry are also relatively fast with just water, so although they start with a handicap after the slurry stage, they are quite capable of catching up. Slow Coticules start with sharper results off the slurry, but they require more work to further refine the edge. Of course, there are not just two categories, but rather two ends of a universe, in which all Coticules are located. It must be clear by now, that every specimen of these natural whetstones asks for a slightly different approach and amount of work required to get the best results.